Silicon dioxide (SiO₂) is one of the most common oxides on the surface of earth. Like most oxides, it adopts a polymeric structure.

An oxide ( /ˈɒksaɪd/) is a chemical compound that contains at least one oxygen atom and one other element^[1] in its chemical formula. Metal oxides typically contain an anion of oxygen in the oxidation state of −2. Most of the Earth's crust consists of solid oxides, the result of elements being oxidized by the oxygen in air or in water . Hydrocarbon combustion affords the two principal carbon oxides: carbon monoxide and carbon dioxide. Even materials considered pure elements often develop an oxide coating. For example, aluminium foil develops a thin skin of Al₂O₃ that protects the foil from further corrosion.^[2]

Formation[link]

Due to its electronegativity, oxygen forms stable chemical bonds with almost all elements to give the corresponding oxides. Noble metals (such as gold or platinum) are prized because they resist direct chemical combination with oxygen, and substances like gold(III) oxide must be generated by indirect routes.

Two independent pathways for corrosion of elements are hydrolysis and oxidation by oxygen. The combination of water and oxygen is even more corrosive.Virtually all elements burn in an atmosphere of oxygen, or an oxygen rich environment. In the presence of water and oxygen (or simply air), some elements— sodium—react rapidly, even dangerously, to give the hydroxides. In part for this reason, alkali and alkaline earth metals are not found in nature in their metallic, i.e., native, form. Caesium is so reactive with oxygen that it is used as a getter in vacuum tubes, and solutions of potassium and sodium, so called NaK are used to deoxygenate and dehydrate some organic solvents. The surface of most metals consists of oxides and hydroxides in the presence of air. A well known example is aluminium foil, which is coated with a thin film of aluminium oxide that passivates the metal, slowing further corrosion. The aluminium oxide layer can be built to greater thickness by the process of electrolytic anodising. Though solid magnesium and aluminium react slowly with oxygen at STP—they, like most metals, burn in air, generating very high temperatures. Finely grained powders of most metals can be dangerously explosive in air. Consequently, they are often used in Solid-fuel rockets.

In dry oxygen, iron readily forms iron(II) oxide, but the formation of the hydrated ferric oxides, Fe₂O_3−x(OH)_2x, that mainly comprise rust, typically requires oxygen and water. Free oxygen production by photosynthetic bacteria some 3.5 billion years ago precipitated iron out of solution in the oceans as Fe₂O₃ in the economically important iron ore hematite.

Oxides, such as iron(III) oxide or rust, which consists of hydrated iron(III) oxides Fe₂O₃·nH₂O and iron(III) oxide-hydroxide (FeO(OH), Fe(OH)₃), form when oxygen combines with other elements

Structure[link]

Oxides of most metals adopt polymeric structures with M-O-M crosslinks. Because these crosslinks are strong, the solids tend to be insoluble in solvents, though they are attacked by acids and bases. The formulas are often deceptively simple. Many are nonstoichiometric compound. In these oxides, the coordination number of the oxide ligand is two for most electronegative elements and 3-6 for most metals.^[2]

The unit cell of rutile. Ti(IV) centers are grey; oxide centers are red. Notice that oxide forms three bonds to titanium and titanium forms six bonds to oxide.

Molecular oxides[link]

Although most metal oxides are polymeric, some oxides are molecules. The most famous molecular oxides are carbon dioxide and carbon monoxide. Phosphorus pentoxide is a more complex molecular oxide with a deceptive name, the formula being P₄O₁₀. Some polymeric oxides when heated depolymerize to give molecules, examples being selenium dioxide and sulfur trioxide. Tetraoxides are rare, one example is osmium tetroxide.

Many oxyanions are known, such as polyphosphates and polyoxometalates. Oxycations are rarer, an example being nitrosonium (NO⁺). Of course many compounds are known with both oxides and other groups. In organic chemistry, these include ketones and many related carbonyl compounds. For the transition metals, many oxo complexes are known as well as oxyhalides.

Reactivity[link]

Oxides can be attacked by acids and bases. Those attacked only by acids are basic oxides; those attacked only by bases are acidic oxides. Oxides that react with both acids and bases are amphoteric. Metals tend to form basic oxides, non-metals tend to form acidic oxides, and amphoteric oxides are formed by elements near the boundary between metals and non-metals (metalloids).

This reactivity is the basis of many practical processes such, as the extraction of some metals from their ores in the process called hydrometallurgy.

Reduction[link]

Metals are "won" from their oxides by chemical reduction. A common and cheap reducing agent is carbon in the form of coke. The most prominent example is that of iron ore smelting. Many reactions are involved, but the simplified equation is usually shown as:^[2]

2Fe₂O₃ + 3C → 4Fe + 3CO₂

Metal oxides can be reduced by organic compounds. This redox process is the basis for many important transformations in chemistry, such as the detoxification of drugs by the P450 enzymes and the production of ethylene oxide, which is converted to antifreeze. In such systems the metal centre transfers an oxide ligand to the organic compound followed by regeneration of the metal oxide, often by oxygen in air.

Hydrolysis[link]

Oxides of more electropositive elements tend to be basic. They are called basic anhydrides. Exposed to water, they may form basic hydroxides. For example, sodium oxide is basic—when hydrated, it forms sodium hydroxide. Oxides of more electronegative elements tend to be acidic. They are called "acid anhydrides"; adding water, they form oxoacids. For example, dichlorine heptoxide is acid; perchloric acid is a more hydrated form. Some oxides can act as both acid and base. They are amphoteric. An example is aluminium oxide. Some oxides do not show behavior as either acid or base.

The oxide ion has the formula O²⁻. It is the conjugate base of the hydroxide ion, OH⁻, and is encountered in ionic solid such as calcium oxide. O²⁻ is unstable in aqueous solution − its affinity for H⁺ is so great (pK_b ~ −22) that it abstracts a proton from a solvent H₂O molecule:

O²⁻ + H₂O → 2 OH⁻

In the 18th century, oxides were named calxes or calces after the calcination process used to produce oxides. Calx was later replaced by oxyd.

Nomenclature and formulas[link]

Oxides are sometimes named according the metal-oxygen ratio. Thus, NbO would be called niobium monoxide and TiO₂ is titanium dioxide. This naming follows the Greek numerical prefixes. In the older literature and continuing in industry, oxides are named by contracting the element name with "a." Hence alumina, magnesia, chromia, are, respectively, Al₂O₃, MgO, Cr₂O₃.

Special types of oxides are peroxide, O₂²⁻, and superoxide, O₂⁻. In such species, oxygen is assigned higher oxidation states than oxide.

The chemical formulas of the oxides of the chemical elements in their highest oxidation state are predictable and are derived from the number of valence electrons for that element. Even the chemical formula of O₄, tetraoxygen, is predictable as a group 16 element. One exception is copper, for which the highest oxidation state oxide is copper(II) oxide and not copper(I) oxide. Another exception is fluoride, which does not exist as one might expect—as F₂O₇—but as OF₂.^[3]

Since fluorine is more electronegative than oxygen, Oxygen difluoride (OF₂) does not represent an oxide of fluorine, but instead represents a fluoride of oxygen.

Examples of oxides[link]

The following table gives examples of commonly encountered oxides. Only a few representatives are given, as the number of polyatomic ions encountered in practice is very large.

See also[link]

Look up oxide in Wiktionary, the free dictionary.

• Other oxygen ions ozonide, O₃⁻, superoxide, O₂⁻, peroxide, O₂²⁻ and dioxygenyl, O₂⁺.
• Suboxide
• Oxohalide
• Oxyanion
• See Category:Oxides for a list of oxides.

References[link]

1. ^ Foundations of College Chemistry, 12th Edition
2. ^ ^{a b c} Greenwood, N. N.; & Earnshaw, A. (1997). Chemistry of the Elements (2nd Edn.), Oxford:Butterworth-Heinemann. ISBN 0-7506-3365-4.
3. ^ Schultz, Emeric (2005). "Fully Exploiting the Potential of the Periodic Table through Pattern Recognition". J. Chem. Education 82: 1649. DOI:10.1021/ed082p1649. 

Emma Louise Hewitt (born in Geelong, Australia) is a singer-songwriter and trance vocalist who lives in Amsterdam.

Biography[link]

Hewitt was the lead singer of the Australian rock band Missing Hours, with whom she released the eponymous debut album in October 2008. The band that she formed with her brother Anthony is currently no longer active, because both now live in Europe and are now working as songwriters of electronic dance music.^[1]

Although Emma Hewitt had a musical background in rock music, she released her debut single in 2007 in the field of progressive house. "Carry Me Away" was a collaboration with British DJ Chris Lake. The single reached number 11 in the Spanish singles charts as well as number 12 in Finland.^[2] The single was a total of 50 weeks in the Billboard Hot Dance Airplay charts in the United States and reached number 1 in December 2007.

After the success of her first single, she has worked with several trance artists such as Cosmic Gate, Gareth Emery, Dash Berlin and Ronski Speed. The single "Waiting", which she published with Dash Berlin in 2009, was ranked 25th in the Belgian singles charts. In Armin van Buurens popular radio show A State of Trance the single was elected by the audience with 2109 votes to the second best song of the year 2009.^[3] At the International Dance Music Awards 2010 "Waiting" was awarded as best HiNRG/Euro Track. She was nominated twice in the category Best Trance Track with "Waiting" and "Not Enough Time".^[4]

Discography[link]

As Missing Hours

• Missing Hours (2008)

As Emma Hewitt

• Burn the Sky Down (18 May 2012)^[5]

Singles

• 2012: Colours
• 2012: Miss You Paradise

Collaborations

• 2007: Chris Lake feat. Emma Hewitt – Carry Me Away (Hot Dance Airplay #1, Global Dance Tracks #28)
• 2009: Cosmic Gate feat. Emma Hewitt – Not Enough Time
• 2009: Serge Devant feat. Emma Hewitt – Take Me With You
• 2009: Dash Berlin feat. Emma Hewitt – Waiting
• 2009: Amurai feat. Emma Hewitt – Crucify Yourself
• 2010: Ronski Speed pres. Sun Decade feat. Emma Hewitt – Lasting Light
• 2010: Marcus Schössow & Reeves feat. Emma Hewitt – Light
• 2010: Gareth Emery with Emma Hewitt – I Will Be the Same
• 2010: Lange feat. Emma Hewitt – Live Forever
• 2011: Dash Berlin feat. Emma Hewitt – Disarm Yourself
• 2011: Allure feat. Emma Hewitt – No Goodbyes
• 2011: Allure feat. Emma Hewitt – Stay Forever
• 2011: Micky Slim feat. Emma Hewitt - Tonight
• 2011: Cosmic Gate feat. Emma Hewitt - Be Your Sound
• 2011: Cosmic Gate feat. Emma Hewitt - Calm Down
• 2012: Dash Berlin feat. Emma Hewitt – Like Spinning Plates

External links[link]

• Official website
• Emma Hewitt discography at Discogs
• Emma Hewitt on Myspace

References[link]

1. ^ beatsmedia.com: Beatsmedia exclusively interviews Emma Hewitt. Accessed 23 October 2010.
2. ^ swisscharts.com: Chris Lake feat. Emma Hewitt - Carry Me Away. Accessed 23 March 2010.
3. ^ A State of Trance, Episode 436. Accessed 23 October 2010.
4. ^ 25th Annual International Dance Music Awards Nominees and Winners. Accessed 27 March 2010.
5. ^ Emma Hewitt Announces Debut Album, BURN THE SKY DOWN. Accessed 2 May 2012.

Eric William Flynn (13 December 1939 — 4 March 2002) was a Chinese born British film and stage actor and singer.

Early life[link]

Flynn was born on December 13 1939 on Hainan, where his father was a Customs officer for the Hong Kong government. After the outbreak of war and the Japanese invasion of China, his family spent several years interned in a Japanese prisoner of war camp (50 years later he would play a British prisoner in Stephen Spielberg's film Empire of The Sun, set in a Japanese prison of war camp in China). He returned to Britain at the age of 13, and was educated at Chatham House School, Ramsgate. He then gained a scholarship to Rada, where he met his first wife Fern.^[1]

Career[link]

Flynn had many television roles. He appeared as Alan-A-Dale in A Challenge for Robin Hood in 1967, as Leo Ryan in the Doctor Who story The Wheel in Space in 1968, as Ivanhoe in a 1970 TV mini series, and as Major Tom Graham in series five of Freewheelers in 1971.

He was also an established musical theatre actor appearing in shows such as Evita, Annie Get Your Gun,^[2] The Sound Of Music, My Fair Lady, A Little Night Music, and Copacabana, starring alongside the likes of Lauren Becall, Maria Freidman, and Suzi Quatro. He originated the role of Bobby in Stephen Sondheim's Company.^[3]

He died of cancer at his home in Pembrokeshire, Wales on 4 March 2002, aged 62.

Family[link]

Flynn was the father of actors Jerome Flynn and Daniel Flynn whom he had with his first wife Fern; the former best known for appearing in Soldier Soldier and the latter known for his character in The Bill.^[4] He also had a daughter, Kerry, from his first marriage. Flynn married his second wife Caroline, a South African, in 1981. Flynn's daughter from his second marriage, Lillie Flynn, finished a three-year acting degree at The Central School of Speech and Drama in 2007 and his son Johnny Flynn is an actor and singer.

References[link]

External links[link]

• Eric Flynn at the Internet Movie Database

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